Abstract：
Synchronous bilateral breast cancers (SBBC) present a considerable issue in external beam radiotherapy because of large fields size and large target volumes. Mono-isocentric volumetric modulated arc therapy (VMAT) appears as an appropriate irradiation technique for these types of tumors. The aim of this study was to demonstrate the utility of a 3D DVH pretreatment quality assurance program in VMAT of SBBC cases. Twenty SBBC patients who underwent radiation therapy in our department were retrospectively enrolled in this study. Fifteen patients were treated exclusively to the mammary glands. Five patients benefited from a dose boost on the tumor bed (60Gy). Nine patients were irradiated on the supraclavicular nodes (50Gy). This dose was delivered in 25 fractions and integrated boost was used when appropriate. Depending on the complexity of the treatment plans; 2 or 4 arcs VMAT plans were used in a mono-isocentric technique. The patient specific quality assurance (PSQA) was evaluated using COMPASS measured data, COMPASS reconstructed (CR) and COMPASS computed (CC) dose compared to treatment planning system (TPS) dose. Clinical evaluation was based on DVH metrics for target volumes and organ at risks. The maximum average dose deviation between TPS, CC, and CR was below 3%. The paired t-test between TPS, CC, and CR shows a strong agreement (p < 0.001). The 3DVH dose distribution comparison between TPS and COMPASS were also performed with good gamma score for global analysis. COMPASS was successfully evaluated as a 3DVH pretreatment system for SBBC despite the large fields size and complex target volumes. It allows the verification of the plan in 3D patient anatomy and the evaluation of dose discrepancies.
摘要：
同步双侧乳腺癌（SBBC）在外束放射治疗中存在相当大的问题，因为大的视野和大的目标体积。单等中心体积调节电弧疗法（VMAT）似乎是这些类型肿瘤的适当辐照技术。这项研究的目的是证明3DDVH预处理质量保证计划在SBBC病例的VMAT中的实用性。本研究回顾性纳入了20例在我科接受放射治疗的SBBC患者。15例患者仅接受乳腺治疗。五名患者受益于肿瘤床上的剂量增加(60Gy)。9例患者在锁骨上淋巴结（50Gy）上接受了照射。该剂量以25个部分递送,并且在适当时使用综合加强。根据治疗计划的复杂性，在单等中心技术中使用2或4弧VMAT计划。使用COMPASS测量数据评估患者特定质量保证(PSQA)，与治疗规划系统(TPS)剂量相比,COMPASS重建(CR)和COMPASS计算(CC)剂量。临床评估基于目标体积和有风险器官的DVH指标。TPS之间的最大平均剂量偏差，CC,CR低于3%。TPS之间的配对t检验，CC,和CR显示出很强的一致性(p<0.001)。TPS和COMPASS之间的3DVH剂量分布比较也以良好的伽马评分进行全局分析。尽管视野大，目标体积复杂，但COMPASS已成功评估为SBBC的3DVH预处理系统。它允许在3D患者解剖结构中验证计划并评估剂量差异。
